1. Field of the Invention
The present invention relates to artificial hair which looks like natural hair and keeps its shape well, and it also relates to a process for producing the same.
2. Description of the Prior Art
Wearing a wig is a common practice to hide one's bald head or lack of hair. Wigs of natural hair have been predominant presumably because people believe that they look natural. Unfortunately, this belief is groundless. Natural hair growing on one's head is entirely different from that attached to a wig.
Natural hair, like wool, is covered with a flaky substance called cuticle. This makes it difficult to use natural hair for a wig. The flakes of cuticle on live natural hair are regularly arranged in one direction and hence permit smooth combing. Once natural hair is removed from one's head, it becomes randomly arranged and entangled. To eliminate this trouble, natural hair is treated with a chemical for the removal of cuticle before it is used for a wig. The chemical treatment adversely affects the gloss of natural hair. Moreover, natural hair without cuticle loses strength and durability when it undergoes sterilization and decoloring. The absence of cuticle permits natural hair to absorb water, making natural hair to feel sticky and hard to handle. To remedy this shortcoming, the entire surface of natural hair is coated; but coating is not so effective as to eliminate the disadvantage of chemically treated natural hair that lacks stiffness and loses the hairdo pattern soon. Thus a wig of natural hair gets out of shape easily in a rainy day or windy day.
To eliminate the disadvantage of natural hair, modacrylic fiber was investigated as a synthetic fiber to replace natural hair. It is not satisfactory in settability, however. As a synthetic fiber for general use, polyester fiber is best. A disadvantage of polyester fiber is that it strongly reflects light and produces an undesirable glossy appearance. The light reflection results from the high refractive indexes. (About 1.72 in the direction of the fiber axis and about 1.54 in the direction perpendicular to the fiber axis.)
There has been proposed a variety of processes for producing a synthetic fiber for artificial hair having an improved gloss. One of them is disclosed, for example, in Japanese Patent Publication No. 40689/1973. According to this process, the synthetic fiber is incorporated with a polyalkylene ether compound in the production stage. Subsequently, the fiber is treated with a solvent which dissolves the polyalkylene ether compound but does not dissolve the fiber. After the treatment a myriad of microscopic voids are formed in the fiber. They make the synthetic fiber resemble natural hair in luster and hand.
In the case of ordinary 0.5-5 denier fiber for clothing, voids in fibers make the dyed fiber look whitish. However, this does not apply to thick fiber (30 to 70 denier) having microscopic voids, 1 to 0.5 .mu.m in diameter, in which case the dyed fiber does not look whitish but retains a bright color. Unfortunately, it is difficult to form microscopic voids in fibers in an accurately controlled manner, and the polyalkylene ether compound causes the dyed fiber to discolor on account of its extremely poor light resistance.
On the other hand, EP137925A discloses a process for treating polyester monofilaments with an alkaline solution, thereby roughening the surface of the monofilaments through leaching and etching. The roughened surface produces the effect of scattering and refracting light. This process, however, is not satisfactory to impart a natural luster to the monofilaments because the mere alkali treatment produces an excessively rough surface.
It is an object of the present invention to provide polyester-based artificial hair resembling natural hair in luster and hand and superior in color fastness to light.